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1answer
176 views

In a moving bus will the ball fall behind me when tossed?

Using Newton's law I have to find whether in a moving bus will the ball fall behind me when tossed in air or will come to me only or will fall in front of me. In fact there are two cases; 1- Bus ...
0
votes
1answer
47 views

What does this term G+G'->G' mean?

In this document, what does the line "Write $\vec{G}_i + \vec{G}_i' \rightarrow \vec{G}_i'$" after equation (25) actually mean?
2
votes
2answers
3k views

How to find the compression of a spring attached to an object [closed]

I am having some trouble figuring out the equation needed to solve this problem. A 3.0-kg block slides along a frictionless tabletop at 8.0 m/s toward a second block (at rest) of mass 4.5 kg. A ...
0
votes
0answers
100 views

Correct way to calculate torque produced by axle

For my electrical engineering course, we had to build a simple DC motor that can lift a coin. I have tested the motor, and here are the results: rotational speed (no load): 3630 RPM (380 rad/sec) ...
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0answers
97 views

Quantum Hamiltonian commuting with the Pauli-Runge vector

I have to prove that $[A_j, H] = 0$, with; $$\vec{A} = \frac{1}{2Ze^{2}m}(\vec{L} \times \vec{P} - \vec{p} \times \vec{L}) + \frac{\vec{r}}{r}$$ $$H = \frac{p^2}{2m} - \frac{Ze^2}{r}$$ And, $Z, e, ...
-1
votes
1answer
155 views

Ball on a slope [closed]

I have a lab report, but I can not write it in a correct way. The lab experiment was about a ball rolling on a slope, I have a height of the slope, the distance, and the time in which the ball spent ...
2
votes
1answer
120 views

Circular motion problem? [closed]

I am learning about circular motion and not quite sure how to approach this particular problem. Any help would be greatly appreciated! A particle moves along a circular path over a horizontal ...
2
votes
2answers
209 views

Mathematical model for this graph of a simplified binary star system?

Unnecessary background for question: I had a school assignment asking us to relate a quadratic equation to a real life example relating to our future dream career, making sure to express the accuracy ...
0
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1answer
57 views

Is it possible to reach lower temperatures than the Boyle temperature in de van der Waals equation?

We know that for a real gas we can write a virial expansion in powers of $p$: $$pV=Nk_{B}T+B(T)p+\cdots$$ It results that the van der Waals equation: ...
3
votes
0answers
134 views

Fock Subspaces and Weight Vectors

This is my first time taking a physics course (I'm a mathematics major), so I'm encountering a lot of new things, which I'm kind of expected to know. In particular, how to work with Bosons. I've got ...
3
votes
4answers
1k views

Time period of simple pendulum with varying mass

How do you find time period as a function of time for a simple pendulum that is in the form of a hollow sphere that is filled with mercury and there is a hole in the bottom through which the mercury ...
0
votes
1answer
548 views

Solve a problem of work and energy

A man pulling sled of his daughter by a massless rope, climbing a snowy hill whose slope is equal to 15 °. Considering that the mass of the sled is $4Kg$, the girl's $26Kg$ and $\mu _c = 0,25$, ...
1
vote
1answer
369 views

Two-block system connected to a spring

Say you have two blocks with masses $m_1$ and $m_2$, where $m_1>m_2$. The smaller block sits atop the larger block. The larger block is connected to a spring, which is then connected to a wall a ...
3
votes
1answer
399 views

Deriving the rocket equation

Recently I decided to brush on the those parts of classical mechanics that always gave me trouble. One of those parts was the rocket equation so I figured that I would try to derive the appropriate ...
-1
votes
1answer
88 views

Normal force at the bottom [closed]

A solid sphere of mass $m$ is released from rest from the rim of a hemispherical cup so that it rolls along the surface. If the rim of the the hemisphere is kept horizontal, find the normal force ...
0
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0answers
45 views

Stagnation point from complex potential

I just wanted to see if I am doing this right. $$\Omega(z) = U(z+\frac{a^2}{z})$$ So to find the stagnation point: $$\Omega'(z) = U(1-\frac{a^2}{z^2})=0$$ Therefore stagnation points occur at: ...
2
votes
0answers
66 views

Spin of a decay product

A particle A decays into particles B, C and D. The spin of A, B and C particles is 1/2 each. What are the possible spins of particle D? My attempt is the following: Since B and C have spin 1/2 ...
1
vote
0answers
120 views

Question about moments? [closed]

Take a look at this diagram: http://www.chegg.com/homework-help/questions-and-answers/7-pipe-assembly-supports-vertical-loads-shown-determine-components-reaction-ball-socket-jo-q2260091 If you ...
0
votes
0answers
222 views

A force F pushes an inclined plane M with a block on the incline; find acceleration up the incline

So there is an inclined plane of mass $M$ that is pushed with a force $F$. A block of mass $m$ is on the inclined plane that accelerates up along the inclined plane due to the pushing of $M$ by force ...
1
vote
1answer
1k views

How to find the wavefunction that solves an infinite square well with a delta function well in the middle?

Solutions for the wavefunction in an infinite square well with a delta function barrier in the middle are easily found online (see here for an example). I am wondering what the wavefunction is for an ...
0
votes
1answer
73 views

Simple circuit with resistances

I have a question about a circuit that I made in class! So, we had a circuit with 2 resistors, one of $R_1 = 330 \Omega$ and one of $R_2 = 470 \Omega$. The tension applied to the circuit should be ...
0
votes
3answers
610 views

Resistive force proportional to velocity

Find the displacement and velocity of horizontal motion in a medium in which the retarding force is proportional to the velocity. I kind of understand how to do this problem. We know that the ...
1
vote
2answers
444 views

Does the velocity of a falling object increase as the mass of a object increases?

I am doing an experiment to show the effect on the velocity of a falling mass due to change in mass. How can i justify my prediction that the velocity of the falling mass will increase as i increase ...
0
votes
2answers
390 views

Finding the velocity of a block down an incline plane after in moves a distance $x_0$

Consider a block sliding down an incline plane at an angle $\theta$ with the horizontal. For the acceleration as a function of $\theta$ I find $$\ddot{x}=g \ \sin\theta $$ My text then claims we can ...
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0answers
39 views

What are some common errors when it comes to measuring hall voltage of a semiconductor?

What are some common errors when it comes to measuring hall voltage of a semiconductor? I've thought of two errors: Adjusting the potentiometer so that the width of the conductor would start with 0 ...
0
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1answer
162 views

Magnification for a concave mirror

Here is the question as given in my textbook: Find the distance of the object from a concave mirror of focal length 10 cm so that the image size is 4 times the size of the object. The solution ...
2
votes
1answer
123 views

Finding Interstellar Extinction Coefficient

I have the following problem for an astrophysics course: A star is seen through a rather dusty region of space has its brightness dimmed by +1 magnitude/kpc, which makes it seem further away ...
2
votes
1answer
162 views

Gravitational binding energy and integrated potential energy not the same?

Before looking up the formula for the gravitational binding energy of a uniform sphere, I simply figured that the general formula for binding energy of an arbitrarily-shaped mass distribution would be ...
3
votes
1answer
283 views

Quantum Mechanics and the Airy Function, the physics of the turning point

I'm working with the Airy function, and the book states at $x=0$ is a turning point, and there are two very different behaviors on either side. In general what a does a turning point mean in ...
1
vote
1answer
699 views

Two hanging masses connected by springs

I had this problem for a candidacy exam, but wasn't able to get the complete answer. Their spring constants and masses are not the same, find the equilibrium position and frequencies of the system. ...
-3
votes
1answer
79 views

combination of 5 identical capacitors [closed]

Given 5 identical capacitors, each EMF. Draw the proper combination of all these 5 capacitors.. 1.) 2.5 2.) 4.17 I really do not know how to solve this thing and if anyone of you knows the title of ...
3
votes
2answers
111 views

Circumference of a circular path

Suppose a car moves with a constant speed of $20 \text{m/s}$ a quarter of a circle, and completes the quarter in $5$ seconds. One way to calculate the circumference is simply $20 \cdot 5 \cdot 4 = 400 ...
0
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0answers
98 views

g as a function of Theta

I slide an object down a ramp of a certain length, which is inclined at a certain angle $\theta$. It reaches the bottom in time $t$. Assuming that no forces act on the object other than gravity and ...
2
votes
1answer
537 views

Momentum variance in momentum space for particle in a box

My assignment asks me to compute the momentum space wavefunction of the nth energy eigenstate of the particle in a one-dimensional infinite square well, then "show that your result is in agreement ...
0
votes
3answers
104 views

Transmission Lines + DC Current

I have a problem where I'm given a circuit that looks like: It contains a transmission line with a characteristic impedance $Z_0$, a source resistance of $R_s$, and a load impedance of $R_L$. If ...
2
votes
1answer
62 views

Velocity from velocity potential

I have this homework question and I get a different answer to the solutions. In Cylindrical polar coordinates $(r,\theta,z)$, the velocity potential of a flow is given by: $$\phi = ...
1
vote
1answer
944 views

Where does the energy of a light bulb come from?

Where does the energy of a light bulb come from? Is it from the coil of wire, magnet in the generator, mechanical input to the generator or plug where the generator is connected to the wall?
0
votes
0answers
86 views

Why does an armature of a generator rotate?

Why does an armature of a generator rotate? a) like poles repel b) unlike poles attract c) current flows up d) an outside force turns it I am thinking that (d) is the correct answer but ...
1
vote
3answers
118 views

Will the rms current be affected by inserting dielectric in the capacitor in an LCR circuit?

MY thoughts: I think it will not be as the expression for RMS value is dependent only on the peak value of current. Is my thinking correct?
1
vote
2answers
128 views

Forces, Incline, and Mass

A farm tractor tows a $3900 kg$ trailer up a $16^\circ$ incline with a steady speed of $3.0 m/s$. What force does the tractor exert on the trailer? (Ignore friction.) I am having trouble ...
1
vote
0answers
226 views

Forces on two boxes

This is a problem from my problem sheet but we haven't yet covered the material or received our books. There is a small box of mass $m_{1}$ resting on a plank, of mass $m_{2}$ and length $L$, which ...
0
votes
1answer
263 views

Height of projectile above the inclined plane and above the horizontal.

I am trying to work out the maximum height of a projectile above the incline plane and above the horizontal plane but I am not sure how to do this. I have worked out all the equations of motion, $ax, ...
2
votes
2answers
79 views

Integration of 3-momentum

During a lecture that I missed, I was trapped when the lecturer uses the relation $$dp_x~ dp_y ~dp_z ~=~d^3\mathbf{p} ~=~ 4\pi p^2 dp.$$ Can I know how is this relation derived please?
0
votes
1answer
78 views

Vector Summation [closed]

When two vectors are sketched from a single point, the angle between them is θ. Show that the size of their vector summation is given in the expression: $ \sqrt{A^2 + B^2 +2ABcosθ} $. Any ...
-4
votes
2answers
355 views

Basic Physics Question [closed]

I'm having a difficult time answering this question. I think I'm just converting the units wrong somewhere: You're the CEO of a courier company, and you decide to select an electric car for your ...
2
votes
2answers
123 views

Scalar QFT Fock Space

I want to demostrate the following relation of the normal ordered product: $\Omega\equiv:\exp{\left(-\int d^3k~a^{\dagger}(k)a(k)\right)}:=|0\rangle\langle0|.$ I proved the commutation relation ...
0
votes
1answer
92 views

How does volume of water in closed system relate to humidity at 25(C) degrees

If I have a closed system with a volume of 100L, at ~24(C) or ~75(F) degrees, what volume must be filled with water to reach a humidity of 90%? I imagined if you fill it 100% with water, humidity is ...
0
votes
1answer
76 views

Loop Rule Parts Problem

[Loop Rule Diagram] The problem is thus: Apply the loop rule to abcdefghia and find the expression which adds to zero. I tried this, but I was not able to get it correct. I know that when crossing ...
2
votes
2answers
246 views

Would this box on the floor rotate based on friction?

There is a floor that friction is proportional to its velocity (like $F=-kv$) and there is a box with its width as $l$ and its height as $h$. (you may assume that $l$ is longer than $h$). It is on the ...
0
votes
3answers
3k views

Calculate average acceleration without time? [closed]

I have a question about a flea jumping, for which I need to show that the average acceleration is around 1000 $ms^{-2}$. I know that to calculate average acceleration you can use $\frac{dv}{dt}$, ...